In the mid 1950s, padded head restraints added to the top of car seats were proposed to reduce injuries incurred during rear-end collisions. Investigators at that time suggested that the primary mechanism of injury in rear-end impacts was hyperextension of the head on the cervical spine. This theory was accepted and acted upon. The National Highway Traffic Safety Administration made it a requirement for all cars made in the United States to have head restraints. Federal Motor Vehicle Safety Standard 202 made this official in 1969, and it has remained unchanged.
In the mid 1990s, several automotive manufacturers attempted to develop more efficient designs that are higher and closer to the back of the head. This was done to prevent hyperextension of the head and neck to conform to what was believed to be a good head restraint position. However, in an accident analysis study conducted by the Transport Research Laboratory, Berkshire, United Kingdom, and the University of Manchester, Hope Hospital, Manchester, United Kingdom, the benefits of good head restraint positioning could not be clearly demonstrated. The data in rear-end collisions, where the benefits of a well-positioned head restraint should have been clear, indicated that a larger distance from head to restraint was associated with lower disability. This study suggests that other injury mechanisms are at work during whiplash.
Certain faulty premises continue to exist regarding rear-end, low-speed collisions. One of these is that whiplash injury is caused by a typical hyperextension movement of the head and neck. In the normal extension movement, the head rotates on the vertebra below C1, C1 rotates over the instantaneous axis of rotation of C2, and then C2 rotates on the C3 instantaneous axis of rotation, and so on until the entire cervical spine completes its full extension motion. In rear-end collisions, this pattern of extension motion does not occur; rather, a completely unnatural motion is observed when high-speed x-ray is used to observe human aberrant spinal kinematic motion. These studies observe axial loading from thoracic spine straightening, causing impaction of the cervical facet plates above and, then, hyperextension of the lower cervical vertebrae rotating and compressing each vertebra from under the vertebra above. This is initiated by the seat back, which is sweeping the lower portion of the neck under the upper portion of the neck. This results in an abnormal double harmonic curve in the cervical spine often referred to as the dreaded “S” curve.
Investigation contributed to the understanding of injury mechanism by identifying the zygapophyseal joint as the source of pain in 54% of patients with chronic neck pain after whiplash injury. With the zygapophyseal joint identified as the primary injury site, the next development was observation of what happened to these cervical joints during the rear-end impact event on human volunteers. This was accomplished with cineradiography, which showed significant aberration in motion during rear-end impact, resulting in facet plate collision and impingement. Increased shear force and extension motion to the lower cervical vertebra was observed while the upper portion of the cervical spine followed the head into flexion, giving the formation of an “S” curve. The transition area of the S curve was at the level of C4, C5, and C6, the most common injury sites observed in a whiplash victim in postaccident x-ray analysis.
Many variables can influence the forces to the spine that can cause injury: the size of the vehicles, the size of the occupants, and the speeds of the vehicles. Attempting to prevent whiplash injury thus can be a daunting task. However, reducing the global movement of the entire spine and the relative movement of each vertebra appear to be the most practical approach in the prevention of injury to the spine. To accomplish this, all spinal curves should be supported and decelerated at as close to a zero delta velocity as possible. This requires support systems within head-neck restraints and seats that are contoured to the spine to reduce the spinal straightening observed during rear end impact. Additionally, the head-neck restraint and seat back should have complementary dampening characteristics so that simultaneous deceleration of the head, neck, thoracic, and lumbopelvic areas can be achieved.
It may be noted in the last connection, that the construction of most prior art seatbacks and head restraints incorporate materials that in an effort to provide maximum comfort, are highly resilient. Such materials while they may absorb some of the impact energy which is generated as the passenger is thrown rearwardly against the seat during a rear end impact, promptly transfer the absorbed energy back to the passenger, causing a rebound effect, which only adds to the detrimental conditions which foster injury.
In accordance with the foregoing, it may be regarded as an object of the present invention, to overcome the problems and disadvantages of known apparatus for preventing whiplash, such as vehicle head restraints and seatbacks.
It is a further object of the present invention, to provide apparatus of the foregoing type, which includes means for efficiently and safely absorbing impact energy, thereby further diminishing the likelihood of passenger injury.
In my issued U.S. Pat. Nos. 5,181,763 and 5,290,091, the entire disclosures of which are hereby incorporated by reference, apparatus is disclosed for preventing whiplash-related injuries to a passenger in a vehicle. The characteristic shapes of the devices shown therein define a supporting means and contour located behind the cranium and cervical spine of the passenger that interfit with the posterior contour of the passenger's cranium and cervical spine. The supporting means interacts with the passenger during rear end impact to maintain the pre-collision shape of the supported spinal curves, to thereby aid in the avoidance of whiplash and similar injuries.
In my further issued U.S. Pat. No. 5,580,124 (the entire disclosure of which is hereby incorporated by reference) there is disclosed a vehicle-installed supporting seat for a passenger, which includes a seat back provided with an integral head-neck restraint comprising a cranium support portion and a cervical spine support portion. Each said portion includes a layer of resilient material supported on an underlying inflexible support shell, which together act to effectively define a contour that interfits with the posterior contour of the passenger's cranium and cervical spine. The support shell is rearwardly displaceable upon being subjected to impressed forces generated from the passenger pressing against the restraint as a result of a rear end impact at said vehicle. A controllably deformable energy absorbing crush zone is disposed to the rear of the shell as to be compressed by the rearward displacement of the shell. The interfitting contour and thereby the inflexible shell, upon being displaced by said forces toward the underlying crush zone, retain the shape of the contour, whereby the cervical and cranium support portions act to substantially simultaneously decelerate the cranium and cervical spine of the passenger during a vehicle rear end impact, while the controlled deformation of the crush zone absorbs energy, to prevent whiplash-related injuries to the passenger.
The apparatus of the U.S. Pat. No. 5,580,124 patent preferably further includes a thoracic and lumbar spine support portion which are defined by downward extension of the support shell, resilient material and contour; whereby the thoracic and lumbar spine portion of the passenger are decelerated with the cranium and cervical spine during a rear end impact.
The thoracic section of the human spine is believed to be compressed and flattened during a rear end impact. In addition to being injured, this flattening of the thoracic spine causes axial loading into the cervical spine as the weight of the head and upward pressure of the flattening thoracic spine serve as end point forces to damage the cervical spine. Where present, the thoracic portion of the above seat serves to prevent the flattening of the thoracic spine by having a kyphotic or concave firm contoured shell that takes the shape of the human thoracic spine and maintains this shape during rear end impact. This firm contoured shell precedes the crush zone material which plastically deforms and produces a controlled damping of the forces incurred during a rear end collision.
The lumbar section of the seat will conform to the lumbar spinal curves of the human anatomy. The initial foam that contacts the occupants is combined with the crush zone feature to maximize the energy absorbing feature of this technology.
This firm contoured shell will hold its form on impact from the rear end collision. This contoured shell will then plastically deform the crush zone material. The function of the crush zone, whatever materials are used, is to initiate a controlled damping of forces that result in little or no rebound energy to the occupant.
The crush zone may comprise one or more air bladders, and valve means responsive to rear end vehicular impact to enable the one or more bladders to at least partially deflate. The inflexible shell can, for example, be linked to one or more mechanical actuators which open the valves upon a predetermined displacement of the shell; or one or more sensors can upon detecting a rear end impact, actuate the valves to enable controlled deflation of the air bladders.
Similarly, one or more rear impact sensors can enable control signals upon an impact of sufficient magnitude, which signal disables a restraint means, e.g. by releasing a mechanical stop which otherwise prevents displacement of the inflexible shell (or of a plate linked to the shell) against or into the crush zone.
In another aspect of the U.S. Pat. No. 5,580,124 disclosure, the crush zone can comprise an impact collapsible cellular structure, such as a frangible foam. In still a further aspect, the crush zone may comprise an elastically deformable material which absorbs energy at a substantially more rapid rate than it releases same.
The crush zone may be sandwiched between the inflexible shell and a spaced fixed, rigid plate; or the crush zone can be spaced from the rear of the shell and contacted and compressed by an intermediate plate which is linked for displacement with the shell. Rearward displacement of the shell may be resisted by restraining means adapted to collapse at a preset strain.
In my further issued U.S. Pat. No. 5,769,489 it is disclosed that the energy absorbing concepts of my U.S. Pat. No. 5,580,124 patent, can be incorporated into a vehicular passenger support in a manner that will independently or conjunctively protect any or all of the passengers' cranium, cervical, thoracic, and/or lumbar spine. Pursuant to that earlier patent, apparatus is thus provided for preventing or limiting spinal injuries to a passenger seated in a forward facing position in a moving vehicle during vehicular impact or sudden deceleration. The apparatus comprises a vehicle-installed supporting seat for the passenger, the seat having a support portion behind the seated passenger which includes a resilient surface in contact with the supported passenger, the resilient portion being supported on an underlying stiff support shell. The support shell is rearwardly displaceable upon being subjected to impressed forces generated from the passenger pressing against the resilient surface of the support portion as a result of a rear end impact at the vehicle. A controllably deformable energy absorbing crush zone is disposed to the rear of the shell as to be compressed by the rearward displacement of the shell, whereby the support portion acts to decelerate the supported spinal curves of the passenger during a vehicle rear end impact, while the controlled deformation of the crush zone absorbs energy, to prevent or limit spinal injuries to the passenger.
The support portion can be provided at a portion of the seat which lies behind the thoracic spine of a seated passenger, and/or at a portion of the seat that lies behind the lumbar spine of a seated passenger; and/or at a portion of the seat which lies behind the cranium and cervical spine of a seated passenger.
The resilient surface may conform to the shape of the spine of the seated passenger. The surface may be preformed to this shape, or may comprise a foam, gel or other material which molds to the contacting body contour of the passenger upon the passenger being seated, and returns to its original shape when the seat is vacated. Materials of this type made of a high density, visco-elastic open-cell material, are available commercially from Tempur-Pedic of Lexington, Ky., and have been used in pillows and mattresses.
The crush zone may comprises one or more air bladders, and valve means responsive to an impact may function to enable the one or more bladders to at least partially deflate upon vehicular impact. The crush zone may also comprises an impact collapsible cellular structure. In another embodiment the crush zone may comprise an elastically deformable material which absorbs energy at a substantially more rapid rate than it releases same. The crush zone can be sandwiched between the stiff shell and a spaced fixed, rigid plate, or can be spaced from the rear of the shell and contacted and compressed by an intermediate plate which is linked for displacement with the shell. Rearward displacement of the shell can be resisted by restraining means adapted to collapse at a preset strain.
In FIG. 1, a cross-sectional view, schematic in nature, appears through prior art apparatus 10 in accordance with the disclosure of U.S. Pat. No. 5,580,124. The vehicle-installed supporting seat for the passenger includes a conventional seating area, which is not shown in the drawing. Extending in a vertically upward direction from the seating area is a seat back 12 provided with an integral head-neck restraint 14 comprising a cranium support portion 16 and a cervical spine support portion 18. Each said portion includes a layer of resilient material 20 supported on an underlying inflexible support shell 22. The material 20 and the shell 22 together act to effectively define a contour 24 that interfits with the posterior contour 26 of the passenger 28's cranium and cervical spine. This contour 26 thus presents a first surface 29 located behind the passenger's cranium for contacting the approximate center of mass of the cranium and supporting the approximate central posterior area of the passenger's cranium, and a second surface 30 located below the first surface and defining a substantially convex smooth curve, the maximum protrusion point 32 of which projects anteriorly relative to where the first surface 29 contacts the center of mass of the passenger's cranium, the said second surface 30 thereby contacting and supporting the posterior portion of the passenger's cervical spine substantially simultaneously with the said contact of the passenger's cranium with said first surface.
The support shell 22 may comprise a hard relatively inflexible plastic, or similarly may comprise metal or the like. The shell may also comprise a relatively rigid foam, one which has high stiffness characteristics, so that such material, as with an inflexible plastic, will maintain the spinal contours under impact loading. Shell 22 is rearwardly displaceable upon being subjected to impressed forces generated from the passenger 28 pressing against the restraint as a result of a rear end impact at the vehicle. In the embodiment shown in FIG. 1 this is enabled by having the shell 22 formed as a front piece 22a and a rear piece 22b, the two pieces being interconnected by one or more flexible accordion pleats, the uppermost of which appears at 34.
A controllably deformable energy absorbing crush zone 40 is disposed to the rear of the shell 22 as to be compressed by the rearward displacement of the shell. The interfitting contour 24 and thereby the inflexible shell 22, upon being displaced by said forces toward the underlying crush zone 40, retain the shape of the contour 24, whereby the cervical and cranium support portions act to substantially simultaneously decelerate the cranium and cervical spine of the passenger during a vehicle rear end impact, while the controlled deformation of the crush zone absorbs energy, to prevent whiplash-related injuries to the passenger.
The second surface 30 of contour 24 is smoothly joined to the first surface 29 by a transition surface 42 of said contour, which extends anteriorly at an obtuse angle from said first surface, and which is located to support the passenger's posterior area approximately where the cranium meets the cervical spine. The maximum protrusion point 32 of said second surface 30 projects anteriorly relative to said flat portion of said first surface 29 a distance of 1 to 6 inches, and the maximum protrusion point 32 is from 3 to 9 inches below the cranium contact zone.
The apparatus 10 preferably further includes thoracic and lumbar spine support portions 46 and 48, which are defined by downward extension of the support shell 22, resilient material 20 and contour 24; whereby the thoracic and lumbar spine portions of the passenger 28 are decelerated with the cranium and cervical spine during a rear end impact.
The crush zone 40 may comprise one or more air bladders, and valve means responsive to rear end vehicular impact to enable the one or more bladders to at least partially deflate.
The crush zone 40 can also comprise an impact collapsible cellular structure, such as a frangible foam. The cellular structure can similarly comprise the well known bubble packing, which is commonly used to protect fragile objects during shipping. Other controllably collapsible or deformable materials can be used for crush zone 40, for example frangible ceramic or organic foams, or the like. The important consideration is that any such materials shall collapse or deform under suitable imposed forces in a controllable fashion so that they not only enable controlled rearward displacement of piece 22a, but also absorb energy in doing so. Thus by way of example, it will be clear that the bubble type packing material referred to absorbs energy during collapse as each of the cells is ruptured due to pressure forces. In still a further aspect, the crush zone 40 may comprise an elastically deformable material which absorbs energy at a substantially more rapid rate than it releases same.
The crush zone 40 may as shown in FIG. 1 be sandwiched between the inflexible shell 22 (via piece 22a) and a spaced fixed, rigid plate 49, which is maintained in its position by support members 23 which extend between plate 49 and back piece 22b. Compression springs 51 may be provided between shell 22 and plate 49 to aid in restoring the original spacing following the controlled collapse of the crush zone. In the variation shown in the partial cross section of FIG. 4, the crush zone 40 is placed to the rear of seat back 12. Here the rearward displacement of piece 22a moves plate 49a which is rigidly linked to piece 22a by members 23a. 
In FIG. 2 a further prior art showing appears which conforms to FIG. 6 in my U.S. Pat. No. 5,769,489 patent. There a conventionally shaped head restraint such as that illustrated can incorporate the principles of the U.S. Pat. No. 5,580,124 patent. Externally head restraint 80 thus has a configuration which is entirely conventional. However the otherwise conventional head restraint is seen to be provided with a resilient support surface 82, an underlying inflexible shell 83, a crush zone 85, and a spaced rigid plate 84, all of which function exactly as has been discussed in connection with the prior embodiments. The shell 83 thus includes the two portions 83a and 83b, with intervening flexible portion 86, whereby upon the passenger's cranium 87 being forced against the head restraint 80 as a result e.g. of a rear end vehicular impact, shell portion 83 is displaced to the left (in the sense of the drawing) against the crush zone 85, which controllably deforms in the manner that has been previously discussed.
Since the head restraint does not have to maintain a specific shape to conform to the passenger's spine, the head restraint can function effectively to limit forces producing head injury, by including merely an outer passenger contacting surface of a foam or other known materials used in the prior art, which surface overlies a controllably collapsible crush zone which the said surface can be displaced against under impact forces. The crush zone can be of the types discussed herein or can comprise other controllably collapsible materials which act to dampen the impressed forces.